On Thu, 13 Jan 2005, N8N wrote:

> > reaction to brake lights is quicker when they are combination
> > brake/tail units. Your way (with P21 bulb) would also take away your
> > sideward visibility of the taillamp/sidemarker, which is definitely a
> > step backwards.

> Any reason for that assertion?

Eyetracker research shows that observers' eyes "prime" on the taillamps
and react faster when a taillamp they're already paying attention to gets
5x brighter, than they do when the taillamp stays the same and another red
light comes on in a different location. The amount of difference is fairly
well related to the distance between the tail and brake functions, which
means Volvo has got it wrong.